This invention relates in general to land vehicles and more particularly, to personal mobility vehicles, such as wheelchairs, scooters, and the like. Most particularly, the invention relates to structural elements suitable for use in wheelchairs that are adjustable to accommodate persons of different sizes.
Adjustable wheelchairs are well known. Some wheelchairs are adjustable to accommodate persons of different sizes. A particular requirement for such adjustment arises when a wheelchair is intended to be used for a child, in which case, the size of the wheelchair needs to be increased as the child grows. While it may be impractical for a single size wheelchair to accommodate a range of sizes of users from a small child to an adult, adjustability of the wheelchair enables use of a single wheelchair to be possible for a number of years before another wheelchair has to be used.
As well as being adjustable, wheelchairs have been devised so as to be foldable from an operative condition to a condition in which side frame structures of the wheelchair are disposed more closely together so that the wheelchair occupies less space. This makes it easier to store or transport the wheelchair when it is not occupied.
A conventional side frame structure typically includes an upper rail member and a lower rail member extending forward and rearward of the wheelchair and substantially parallel to one another. A cross-brace assembly has two cross-brace members pivotally connected to one another by a pivot member. Each cross-brace member has a lower end that is pivotally connected to a respective side frame lower rail member and an upper end that is connected to a respective seat-supporting member. Links are pivotally connected between the cross-brace members and respective upper rail members of the side frame structures. To provide the adjustable width of the wheelchair, the cross-brace members and the links are adjustable.
The rail members of a conventional side frame structure are typically in the form of tubular metal, joined at front and rear by spaced upright members, which commonly include plastic moldings. The upright members at the front of the wheelchair generally support front wheels, usually castor wheels, and footrests, leg rests, and/or other devices that are commonly found at the front of wheelchairs. The upright members at the rear of the wheelchair may support rear wheels, seatbacks, attendant handles, and other items commonly found at the rear of wheelchairs. The rail members, which are circular in external cross-sectional shape, engage as a close fit in correspondingly-shaped receiving formations in the upright members, and are held in the receiving formations by fasteners extending transversely from the upright members and diametrically through the rail member parts received therein. The circular external cross-sectional shape of the rail members is, of course, convenient for pivoting of the cross-brace members and the links of the cross-brace assembly thereabout but has a disadvantage in that the connections with the upright members might become slightly less than fully tight and rigid over an extended service life of the wheelchair. In particular, “working” of the fasteners passing through the rail member parts and the plastic moldings which receive the rail member parts might permit the rail members to twist about a longitudinal axis within the receiving formations.
What is needed is a structural assembly wherein relative movement between rail members and upright members of a wheelchair side frame is prevented but a pivotal connection of cross-brace members and links about the rail members can be provided.